The present invention refers to a method to control the speed of a vehicle by means of a cruise control, substantially by setting the cruise control at least in one of: a cruise control state, in which the speed of the vehicle is controlled, preferably with regard to a selected constant speed; a retardation state, in which the speed of the vehicle is controlled towards the selected constant speed, an acceleration state, in which the speed variation is preferably manually controlled, a distance control state, in which mainly a vehicle""s distance to another vehicle in the travel direction of the vehicle is controlled and an inactive state, in which the system is temporary or permanently switched off.
The invention also refers to a cruise control system.
A cruise control is a convenience means in a motor vehicle to hold a constant speed during shorter or longer driving distances. Generally, the cruise control is switching on by actuating a special start of set button at a certain speed. The speed of the vehicle at the switch-on moment is stored in a memory and the cruise control controls the speed of the vehicle with respect to the stored value. The cruise control is switched off by means of a termination button or for example by actuating the brake or clutch petal. The cruise control can be restarted by actuating the start button at a certain speed or pressing a resume button, which restores the cruise control for the speed that it was initiated for before it was switched off.
A conventional cruise control system consists of a computer unit, which is connected to sensors, which for instance are provided to read and report the engine condition, the position of the accelerator, clutch and brake pedals and other relevant information to the computer unit. The computer unit is also connected to means for controlling the motor, for example by decreasing or increasing the fuel feed to the motor. Additionally, the computer unit is equipped with memory units for storing instructions and other temporary information.
There are different devices to determine the distance to an object or its speed. Examples of such devices are laser cameras, cameras and radar. The rapid development which the radar technique has resulted in dimension reduction for radar equipments including equipment for signal processing, in such a degree that also different types of vehicles, such as private cars, trucks and buses can be equipped with a radar equipment, for example as an extra precautionary measure, for navigation objectives etc.
There are also cruise control systems, in which a radar is connected to the cruise control system, which for example provides the system with distance or speed with regard to a vehicle ahead. This system allows controlling the speed of the vehicle with regard to a distance to the vehicle ahead. A problem with this cruise control system is that it lacks a possibility, specially in an intelligent way stop an unwanted acceleration of the vehicle in a safe way.
The main objective of the invention is to provide an improved cruise control arrangement, which essentially with regard to the speed of another vehicle, preferably in the travelling direction of the vehicle, controls the speed of the vehicle so that no unwanted acceleration can occur.
Above-mentioned objective is achieved through a method, according to the preamble, which sets the cruise control in an additional state in which the speed at the transition time to this state is maintained.
A cruise control system according to the invention includes a computer unit, sensors and control devices. The computer unit when activated controls the speed of the vehicle by means of the control devices and with regard to a selected speed as well as information obtained from the sensors regarding the distance and/or speed of another vehicle ahead. By indication from a distance and/or speed sensor that the vehicle ahead departures from the sensing field of the sensor and that no other vehicle is within the sensing field, the computer unit is arranged to assume a temporary state, in which the speed of the vehicle at the changeover to said temporary state is maintained.